Color mixer



fMarch 1 1927 H. GfUENDl-:R

COLOR MIXER Filed Apr`1l-28, 1924 2 Sheets-Sheet 1 E ffzz bef? Grue 2262er March 1 1927. l

H. GRUENDEr COLOR MIXER Filed April V28, 1924 2 Sheets-Sheet 2 Patented Mar. 1, 1927.

l; UNITED ASTATI-:s

PATENT OFFICE.

y' Aminnaar GRUENDER, or sfr. Louis, MIssoUnI, Assiduo?. To enormenY FABYAN, or

' GENEVA, ILLINOIS.

coLoRy MIXER.

i lApplication filed April 28, 1924. Serial No. 709,388.

This invention relatesI tothe mixing Vor blendingfof colors At the-present time the best method available is that .which makesuse of' rapidly ro- .V tating discs having sectors of different colors.

This .method` has Yvarious disadvantages. y In therstfplace it does not mix colors,

' that is, it does not produce a physical mixture ofdifferent colored lights. Vhen We 1o rotatey afcolordisk, the different colored lights Whichf'are reflected from its severall sectorsrem'ain distinct and` separate just asI they are When the disk is at rest. l/Vhat the color Wheel really does is to present, in rapid succession",v .fto'` the same retinal elements, those'amountsandkinds of light which are reflected from the several'sectors.

i AnotherV disadvantage of the color Wheel i'sthat many colors produced by. it are of a rather.' 10W degree of saturation. Thus, for instance, 4.theV 'combination j in appropriate Y proportions of red and'green onY the color Wheel resultsin a rather greyishyellow.

'2A third-*disadvantage of the color Wheel method is `thatvve can never' see the exact components which' enter into a mixture. This holds' true veven when all the colored sectors y*are of equall size. For We must imagine that the light which is reflected from each 'sector isspread uniformly over 'i l [the Whole disc, that is, over 360 degrees. v'But if "the light Which isreflected from any particular sector Werethus spread uniformly over 360 `degrees, it"yvould vproduce a very different color sensation from that Which is produced byfthesame sector at rest.

,ff-It is'an obje'ct5therefore, Vof the present Vinventionto.provide a ltrue color mixer.

furtherobject is ,tov provide simple Ameans; for varying to apredetermined extent ,Y the'intensity of each constituent of a beam of mixed colored lights. 'Other' and further important objects of this invention'will be; apparent from the disg .45' closuresin the drawings and specification.

The/invention (in a preferred form) is illustrated in 'thel drawings and hereinafter 1 more `fully"described.

On the drawings:

Figure l is a side elevation of' a color 50 mixer constructed in accordance with the present invention.

Figure 2 is an end view of the same.

' Figure 3 is `a top plan vieuT of lthe same.

Figure 4 is a section on the line 4 -4 of 55 Figure 3.

Figure 5 is a section on the line 5-5 of Figure 4c. Figure 6 is 'a section on the line 6-6'ot` Figure 4. l f

' Figure 7 is a diagrammatic illustration of the method by Which the colors are mixed.

Figure 8 is a'diagrammatic illustration of' the method by Which the intensity of the individual colors is varied. Y

As shown on the drawings:

Before describing the apparatus embodying the-preferred form ofthe invention the principles of optics on which it is based will be explained. Tf aplainunsilvered sheet 70 of glass is placed in the path of a beam of light at 450 thereto about 10% of the light is reflected` and 90% transmitted. If tWo suchV sheets are superimposed an additional percentage is reflected. VThis additional/.75 amount of reflected light is smaller than the first amount for various reasons: first, the amount of incident light reaching the second reflector is only 90% of the original Vlight and 10% of this is 9.0%; secondj the light 80 reliected from the second reflectorl has to be transmitted through the first andtherefore there is a loss of 10% by Vreflection by the first reflector. This gives as the total increment 8.1%. Other factors enter into the 35 problem and these figures are given merely to illustrate how; as the :number of super imposed reiiectors increases, the proportion of reflected light increases and the amount of transmitted light decreases by sivelyfsmaller increments.

yThis provides a ready means for either adding'lightto or subtracting light from a beam. By using reflected light each. extra mitted light each extra reflector subtracts` succesfrom the quantity of light reaching theI observer.

This is clear from the following table Amount of N o. of superimposed reflectors. Reflected. hgthrlgsd) mitted.

Pr cent. Per cent. 10 90 17. 9 82.1 24. 1 75. 9 29.` 0 71. 0 32. 9 67. l 36. 0 64. 0v

In Figure 8 F1, F2 and F3 represent color screens of the three colors, red, green and blue-violet respectively. M1, M2, M3, m1, m2, and m3 are plain unsilvercd glass reflectorsA or sets of reflectors in thepaths of the beams of light vpassing through the color screens and at O to the latter.

By using a plurality of reflectors at M3V the proportion of blue-violet light will be vincreasedv and at Ythel same time the green and red will be decreased to a lesser extent owing to the smaller amount of transmitted light which a plurality of reflectors will.

allow tor pass as comparedwith only a single reflector.

If it is desired to decrease the green still further a plurality of. reflectors at m2 may be used. In Athis way without varying the intensity of light passing through the color screens, which may therefor-e all be illuminated from a singlev source of white light, the components of the final beam represented.` by the sum of O1, O2 and O3 may be varied. relatively to each other as desired.

The apparatus shown comprises a wooden box 10. provided witha bracket or support 11 so that it will stand tilted up on one edge as shown in Figure 2. The sid-e 12 oppositie to the onev to which this bracket is attached by hinges 13 so that accessmay be had to the interior of the box forv the purpose of changing the slides which carry the reflectors.

In' another side are arranged aseriesl of color filters 14, 15' and 16. See Fig. 4. Over these `filters are a series of hinged flaps 17, 18: and 19 so that anyone or. more of the color. filters may be-covered as desired..r These color filters rest uponabase .23 of two sheets and 24 of three plates. Obviously any number of plates in any combination may be used as occasion requires. Each plate or set of plates may be removable or four permanently fixed plates may be used, as shown, with ledges 25 beneat into which frames carrying additional plates or sets of plates may be inserted as desired. F or convenience in`= operation a silvered mirror 26 is provided in one end of the box to deflect the compositebeam of light out through an aperture 27 in the side 12 instead of projecting it through the end of the box. It is frequently desirable that a direct comparison be obtained between light without a given; component and the same light with such component. To enable this toA bel don-c a rod 2S providedfwith' a handle 35 is slidably mounted in a block 29-fon`fthe\ box so thatfit may be projected over the adjacent color filter 16. See Fig. 7. This rod casts a` shadow' 34. across; the color filter 16 beneath it. Assuming', therefore', that. the

three color screens are: red, green. and blueviolet and that the r0d128f extends over the` latter, the main portion of the image seen through aperture 27 will be composed of a mixture of all-three colors while the center strip will be composed of' only red and green.

The box. is finished dull black on. the interior inrorder to absorb all light reachin ,the sides. Further, partitions 30, 31 an A 32', also dull black, are provided for .keeping separate the light beams passing through the variouscolor filters. An aperture 31. is arranged iny the partition 32 for the passage of the' composite beamof light.

All the reflectors used are thin glass lates of substantially uniform. thickness an size. Conveniently microscopel cover glasses may be usedY for the purpose.

The accuracy of theV results obtained by the apparatus depends upon keeping the reflectors clean. They should never be touched with the fingers as the latter leave'A a film upon the glass and the amount oflight transmitted (or reflected) will vary with the thickness of the film. This instru# ment yis'very sensitiv-ein. this regard.A This inconvenience in handling the instrument maybe readily avoided by providing a. set

of thin uniform frames (3()y or4 more) in.

wl1ich..tliev plates are loosely but permanently enclosed. There should be oney set.A`

ofA such frames containing' one plate; an-

other, each containing twol plates; a'. third,

each containing three plates; and; so forth'. Then the plates, once thoroughly cleaned,

need never be touched. This arrangement ployed such colored gelatine films. Such V` films should each be backed by a thin plate of finely ground glass so Ythat no object can be seen through the films.v The films themselves are the objects observed. In use the instrument is held against the brightly illuminated clouds and the eye of the o-bserver is above the aperture 27. As a result,

' he sees superimposed images of the filters '10:

and the size of the apparatus is such that the lilters'areapproximately atreading distance. vIn some cases, instead of arranging i ground rture 27.

ground glass behind the color lilters, a glass may be placed in the aper- VI amva'ware that many changes may be made, and numerous vdetails of construction may be varied through a Wide range l without ldeparting from the principles of this invent-iomand I therefore do not purpose limlting the patent granted hereon,

otherwise than necessitated by the prior art..

IV claim as my invention:

A device of the kind described comprising a plurality of color screens,a plurality of reflectors of plain unsilvered glass adapted to form a single beam oi' light of a single color composed of the light reflected by each of sai-d reflectors and means for Y HUBERT GRUENDER, s. J. 

